Stegosaurus is a famous Jurassic
herbivore which had large sharp spikes on its tail, which it may have swung
around to inflict deep wounds on an attacking Allosaurus.
The name roof reptile comes from its plates which were once thought to cover its
back horizontally like armor, however recent studies show the plates were
upright. They may have been used to warm it up in the morning if it was cold
blooded, or perhaps it flushed the plates with blood so it stood out pink to
intimidate predators.

Its plates were not attached
to the back bone so it is unknown haw it was positioned. they may have
been arranged in pairs, or in one straight row or in a zigzag pattern
along its back. We just cant tell.